1. Field of the Invention
This invention relates generally to an ink jet printer that uses hot-melt ink. More particularly, the invention relates to an ink jet printer having an ink supply tube which connects a nozzle array and an ink tank wherein the ink supply tube is made of an elastic material that contracts and deforms corresponding to the contractions and deformations of hot-melt ink contained in the ink supply tube when the ink is solidified.
2. Description of the Prior Art
In conventional ink jet printers such as that disclosed in U.S. Pat. No. 4,785,315, an ink supply tube for supplying ink from an ink tank to a nozzle array is made of a rigid material such as metal or plastic and the inlet of the tube into which ink from the ink tank enters faces down.
The ink used in hot-melt type ink jet printers is a solid at room temperature but liquifies when heated. Ink jet printers heat the ink and eject the liquified ink onto paper or another recording medium. These printers have no restrictions on the printing medium, are easy to use, and for these reasons are gaining attention as an effective method of printing.
One drawback of conventional printers occurs when liquid-phase ink solidifies after the heater for the nozzle array and the ink tank is switched off. When the ink solidifies attendant to lowering of the ink temperature to room temperature, its volume contracts and its shape deforms causing air to penetrate between the solidified ink and the walls and bottom of the ink tank and into cracks that form in the solidified ink. When the ink is reheated and melted to a liquid-phase, the air transforms into air bubbles in the liquified ink. With conventional ink jet printers, these air bubbles enter the tube that supplies ink from the ink tank to the nozzles. As a result, when the drive element for ejecting ink applies pressure to the ink by inwardly deforming the wall of the ink tank, the air bubbles in the ink absorb the pressure, thus hindering the efficient ejection of ink.
Another drawback of conventional ink jet printers occurs when ink contracts and deforms as it solidifies. The rigid ink supply tube of conventional ink jet printers allows air bubbles generated in the ink tank to fill space produced in the ink supply tube by the contracting and deforming ink. These air bubbles appear in the ink supply tube as air between the solidified ink and the wall of the ink supply tube. When the ink is reheated and melted, the trapped air reappears as air bubbles in the ink supply tube. When the printing is carried out in this condition, the air bubbles enter the nozzles, adversely affecting the ejection of ink.